Fatehpur Sikri

Akbar built Fatehpur Sikri in red sandstone from 1571 as his imperial seat, complete with palaces, a mosque and a debating hall for scholars of five religions — then left it, most likely because the water supply failed. Nothing was built over it, so the city stands as designed; go on a weekday and walk from the Buland Darwaza gate through to the private quarters.